Electromagnet



Sept. 10, 1946.7 E. A. DERUNGS ELECTROMAGNET Filed Dec. 23, 1945 2Sheets-Sheet 2 Mal/Z07:

ERNEST LPHONSE DERUNGS flmrney Patented Sept. 10, 1946 UNITED STATESBPATENT ()FFICE ELECTROMAGNET Ernest Alphonse Derungs, Le Locle,Switzerland Application December 23, 1943, Serial No. 515,404 In FranceApril 23, 1940 trcmagnet and the object controlled by the same,

for instance, cams for compensating the great differences in the forceof attraction between the moment when the ai is a maximum and the momentwhen it is a minimum. In this case, the loss of energy caused by thedispersion of the lines of force occurring at the beginning of theattraction is not recoverable. Besides this the mechanical device forobtaining a uniform force of attraction to be transmitted represents acom plication diminishing the efiiciency of the appa ratus.

Object of the present invention is to obtain elcctrom-agnet permittingthe force of attract on to be rendered uniform without providingadditional means, while constantly disposing of the required energy at amaximal efliciency.

electromagnet according to the invention comprises two mutually movablecore and armature members approaching each other when the excitingcircuit. is closed, the end portion of at least one of these memberscomprising a number of arranged in steps with surfaces gradually dnishing towards the end of the member, in order, during the mutualapproaching of the members, to obtain a canalisation of the lines offorce and, in consequence, an adjustment of the force of attraction.

In a preferred embodiment means are provided for avoiding a violentshock at the end of the armature stroke. These means are: amplifying theattraction at the beginning of the stroke of the movable armature andreducing it towards the end of the stroke.

The first of these means consists in the form given to the end portionsof the members appreaching each other. By preference, one of thesemembers a staggered end portion which corresponds to a hole of slightlygreater lateral dimensions in the other member.- The steps ofsubstantially regular form can be interconnected by parts whoseinclination is preferably in the order of 45 degrees. The saidcorresponding hole in the other member need not necessarily lit thesteps exactly. The ratio between the cross sections of the end portionand of the cross section of the main body of the armature, as well asthe ratio between the lengths of the difierent steps can be chosen sothat maximal recovery of the leakage lines of the magnetic field isobtained, this, however, within limits in which the force of attraction,owing to the deflection of the lines of force in the interior of thehole, does not show 9 a diminution which is injurious to a reliableworking during the closing of the electromagnet.

The second means consists in the manner of excitation. By preference,the intensity of the exciting current is greatest at the beginning ofthe attraction of the movable armature and gets smaller towards the endof the stroke where the gap is smallest. This variation in the currentintensity can be obtained by well-known means, g. by the use of one orseveral change-over switches operated by the movable armature during itsstroke and by separate circuits which are successively connected inparallel and in series by these change-over switches, or by the use ofany resistances which are connected to the exciting circuit by means ofthese change-over switches.

It is understood that these two means can be used separately and thatthe first one alone can s ecially form a sufficient adjusting means formany applications.

The accompanying drawings illustrate, by way of examples, twoembodiments of the electromagnet according to the invention.

Fig. l is axial section of the first embodiment;

Fig. 2 is a partial plan view of the same,

Fig. 3 illustrates a detail of a switch.

Fig. 4 is an axial section of the second embodiment.

Fig. 5 shows the movable armature and the fixed core in another mutualoperating position, than that in Fig. 4.

Fig. 6 is an elevation, partly in section, of a switching devicecontrolling the excitation of the windings in the second example, and

Fig. 7 is a plan View thereof.

In Figs. 1 to 3 an electromagnet with a movable, central dippingarmature is represented, which is greatly saturated and receives theexciting current from a source of current with practically constantvoltage, for instance, from a storage battery.

As may be seen in Figs. 1 and 2 of the drawings, a tubular, subdividedsteel body ll] of the electromagnet ends on the one side in a steel discH comprising a fixed core l2 provided with a hole i3 ending in a bore M.This hole l3 has a truncated cone portion l5 followed by a cylindricpart l8 and another truncated cone portion IT. The cone angle of theportions l5 and I1, that is the angle between the generating line ofthese portions and the central axis of the electromagnet, is about 45.On the other end the tubular body H! has a steel disc l8 having a flangeIQ for centering the movable armature 2| and at 29 a diameter slightlygreater than that of the flange H3. The movable steel armature 2| ofcylindrical form carries on its outer end a shoulder 22 and on its innerend a truncated cone surface 23 followed by two cylindrical portions 24and 26 interconnected by another truncated cone 25, further followed bya third truncated cone 21 and a cylindrical guide rod 28 slidablyarranged in the bore M of the disc Hence, the section of the inner endportion of the armature 2| diminishes by steps. A spool made of anon-magnetic tube 29 fixed to the core l2 and of two steel plates 36 and3| is centered in the disc |8 by the shoulder 32 of the plate 3| andheld in place by the screw 33. In the annular space 34 are mounted twowindings one of which, made of fine wire, receives the exciting currentdirectly by the conductor 35, while the second one, formed by a thickerwire, receives the current by the intermediary of the conductor 31 fromthe contact 38, the conducting blade 38, the contact 40 and from theconductor 4| in order to be earthed by the conductor 42. A limit switchis formed by the support 43 fixed to the disc II. This support 43carries an axle 44 on which the support 45 can freely rotate. The latteris connected by two insulating. bars 46. 46', on the one side, to theconducting blade 39, on the other side, to the adjustable holder 41 fora draw spring 48. Two columns 49 and 49' fixed to the disc carry theinsulating plate 5i! held by the screws 5|. To this insulating plate 50the two contacts 36 and 40 are fixed, to which the conductors 31 and 4|are connected by the screws 52 and 52. The proportion of the diameter ofthe cylindrical part 2| to the diameter of the portion 24 determines thedegree of uniformity of attraction, and owing to the arrangement of theconical surfaces on the armature and on the fixed core most of theleakage lines lost in ordinary magnets are absorbed by the surfaces I5,25 and 21; however, when the cylindrical part 26 is on the level of thecylindricalart IS, the closing of the lines of force between these twocylindrical parts 26 and I6 remains small enough as not to cause toogreat a diminution of the attraction force of the armature; this is alsothe case when the cylindrical surface 24 is on the level of thecylindrical surface I 6. Besides, in order to augment the effects ofcanalisation of the lines of force, the passage section for the magneticfield in the interior of the tube l0 and in the pieces I8, 30 and 3| ismuch greater than that in the cylindrical portion of the armature 2|.

Operation:Before the beginning of attraction, the electromagnet is inthe position shown in Fig. 1, that is, the armature 2| has the greaterdistance from the core l2. When excitation takes place, the two windingsare connected in parallel. The current passes through the conductor 31,the contact 38, the conducting blade 39, the contact 40 and theconductor 4| through the winding with the thicker wire and the earthedconductor 42, and for the winding with the thin-. ner wire through theconductor 35 and the earthed conductor 36. As above-mentioned, thecurrent density in the thicker wire is comparatively very great and themagnetisation of the armature 2| quickly reaches the limit ofsaturation. By the special form of the inner end portion of the movablearmature 2| constituted by the cylindrical and conical parts 23, 24, 25,26, 21 and 28 the path of the lines of force is shortened with regard tothat which should have been effected by the lines of force in the air;this diminishes by so much the leakage flux which might occur betweenthe cylindrical surfaces of the armature 2| and the tube |6. Inproportion as the movable armature 2| app-roaches the fixed core |2, thepenetration of the cylindrical parts 26 and 24 into the hole 3 tends toreduce the force of attraction owing to the deflection of some of thelines of force in a direction perpendicular to the stroke of the movablearmature 2|. In this way the attraction force is augmented at thebeginning of the movement of the armature and diminished from the momentwhen it attains a value exceeding the prescribed effort to be exerted bythe movable armature. As soon as the armature 2| is at the end of itsstroke and the stop 22 is only at a small distance from the disc l8, therod 28 lifts the support 45 which pivots around the axle 44 and, bymeans of the bars 46 and 46 takes along the conducting blade 39 which isthereby disconnected from the contacts 38 and 40 on which it wassupported by the spring 48. Therefore, the exciting current of thewinding with the thick wire passing through conductor 37, the contact38, the conducting blade 39, the contact 40, the conductor 4| etc. isinterrupted at this moment and the armature is now held in attractedposition by the Winding with the thin wire only, fed by the conductor35; the winding with the thick wire being thus traversed by a currentfor a short time only.

Although the thin wire fed through the conductor 35 produces arelatively small excitation, the excellent utilisation of thisexcitation owing to the armature 2| and the core l2 being broughttogether, allows the armature to be sufficiently held by the thin wirewinding only.

Fig. 4 illustrates an electromagnet which comprises a. movable armatureforming a dipping core 60 cooperating with a portion of the fixed core6|. The inner end portion of the core 6|] presents several partsdiminishing by steps towards the end in the following manner: a firsttruncated cone 62 is followed by a cylindrical portion 63, a secondtruncated cone 64, a cylindrical part 65, a third truncated cone 66, acylindrical part 61, a fourth truncated cone 68, a cylindrical portion69 and by a fifth truncated cone 10. To the end of this armature 60 acentering rod H is fixed, guided in a bore 12 of the fixed core 6|. Therod might even be attached to the fixed core 6| and enter a bore of themovable armature 60. The fixed core 6| has a hole 13 with inner stepswhich, on the movable armature 60 being at the end of its attractionstroke, fit the outer steps of the armature 60. The hole 13 of the fixedcore 6| has thus a truncated cone 14, four cylindrical parts 15, 16, l!and 18 interconnected by truncated cones T9, and 8|, while the part 18is followed by a truncated cone 82. The surfaces of the truncated conesof the movable armature 6D and of the fixed core 6| have preferably aninclination of about 45 with regard to the axis of the electromagnet.

The length of the cylindrical parts 63, 65, 6'! and 09 in axialdirection gradually diminishes towards the inner end of the armature 60,and in an analogous manner, the length of the cylindrical parts of thehole 13 of the fixed core 6| diminishes from'the exterior to theinterior of the hole. Moreover, thedifierence between the cross sectionsof the cylindrical parts 63 and 65 of the armature 60 is smaller thanthe difference between the cross sections of the cylindrical parts 65and 61 and this difierence-is smaller than that between the crosssections of the parts 61 and 69, so that the surfaces of the connectingtruncated cones become higher towards the inner end of the armature 65,for compensating the diminution of the diameter of these surfaces.

Around the fixed core 6| and the movable armature 68 an exciting coilis-arranged which is subdivided into five different windings 83, 84, 85,8 6 and 81. The coil is carried by a tube 88 of non-magnetic materialand two steel discs 89 and 98 and the closing of the magnetic circuit isobtained by atubular steel-member 9|, an annular steel disc 92 and thefixed core 6|. The disc 92 has a flange 93 which, on the excitation ofthe coil, is saturated by the magnetic fiux and prevents a lateraladherence of the movable armature 60.

The excitation of the coil is controlled by means of a switching devicewhich can be operated by hand or automatically in dependence on thedriving moment or on the speed of a machine, or on the time, or on acombination of these means. This switching device preferably operates insuch a way that one can excite at will either the first winding 83solely, or the two windings 83 and 84, or thethree windings 83, 84 and85, the four windings 83 to 86, or all the five windings together. Theswitching device might also be operated by the guide rod 7|. An exampleof a switching device is given in Figs, 6 and 7, allowing the excitationof the windings to be progressively controlled. A frame I08 carriesyieldably mounted contact members I81, Hi2, I83, I04, and I85 connectedto the outgoing lines 83a to 81a of the windings 83, 85, 84, 86 and 81.Said contact members l] to I cooperate with additional contact membersin the form of pivoted arms HI I01, I08, I08 and H8 kept open by springsI28. Each of these arms is operated by rods H6 and H7 acted upon by asingle cam disc possessing a helicoidal part HI and a fiat part H2. Theshaft H3 of this cam disc is mounted in a bearing of the frame Hit andcarries a driving means in the form of a pulley H4. When the cam disc isrotated in the anticlockwise direction, it causes progressively theclosing of all contacts beginning at the winding 83and ending at thewinding 81. When the edge I l2a of the cam disc releases the arms 155 toH8, these latter abut with their ends H5 on the frame I00 while the rodsH6 and Ill take the position shown in dotted lines in Fig. 6. Thearrangement shown in Figs. 6 and '7 insures both an abrupt interruptionof the Contact members when the cam disc releases the rods H5, H7 and acontact pressure which suffices for adequate switching. All windinglines Fig. 4 are connected at one end to the positive pole I of acurrent source and the excitation of each winding is established as soonas the other end is connected to the negative pole by the switchingdevice.

The rest position of the movable armature 68 is approximately that shownin Fig; 4. If, in this position, an electric current traverses the innerwinding 83, a small excitation is produced and the lines of force areformed in the air gap between the inclined surfaces 14 and 64 of thecore GI and the armature 60. Since these surfaces lie relatively closetogether, the small excitation produced by the winding 83 sufiices toattract the armature 68 until the cylindrical surfaces 63 and I5 beginto overlap each other (Fig. 5). In this case the lines of force producedby the winding '83 are deflected perpendicularly to the axis of thearmature 88 and, in consequence, can no longer advance the latter. Ifthe two windings 83 and 84 are new fed with current, the saturation ofthe lines of force in the portion 15 of thefixed core BI is such thatfurther lines of force pass through the air gap between theinclinedsurfaces 66 and F9 and the movable armature is again attracteduntil the cylindrical surfaces 65 and I6 overlap each other and thelines of force are deflected anew perpendicularly to the axis. When thewinding is excited together with the windings 84 and 83, a similarprocess is repeated and so forth until the entire coil is excited andthe movable armature 60 is at the end of its stroke.

From the foregoing it may be seen that by the variation of theexcitation during the displacement of the armature it is possible toobtain a canalisation of the lines of force and an adjusting of theattraction force.

The movable armature can, for instance, carry out the whole stroke in anintermittent movement of any duration whatever. On exciting the fivewindings simultaneously the stroke is carried out in a rapid continuousmovement. On exciting only the inner winding 83, or the two windings 83and 84, or the windings 83, 84 and 85 etc., the armature 68 is displacedup to an intermediary position corresponding to the degree of excitationof the coil.

It is evident that in lieu of utilising a certain number of differentwindings, the variation of the excitation can be reached by a single,nonsubdivided coil which is combined with a variable outer resistanceprogressively connected in by an independent control or by the movementof the rod H.

The described electromagnet might be combined with a device transmittingmovement by means of cams, operating as moment and speed varier, or withan absorbing device (dash-pot).

In order to fi-x the stops between two partial excitations exactly, thesingle steps of the end portions of the armature and the fixed coremight have a saturation flange analogous to the guide flange 93.

The outer end of the armature 5i! has a shoulder 22 destined to comeinto contact with the fixed disc 92 so that between the cooperatingsurfaces of the core 6! and the armature 68 a small air gap is possiblefor acting against the remanence in the fixed core and the armature.This shoulder 22 might be adjustable in order to adjust the period ofremanence when the period of' excitation is controlled.

What I claim is:

1. In an electromagnet, an exciting circuit, a core member, and anarmature member arranged to approach each other when. said excitingcircuit is closed, at least one of said members having a number ofrelatively fixed parts arranged in steps and comprising surfacesgradually diminishing towards the end of member, said member beingdisposedv with regard to the other member in such a cooperating positionthat during the mutual approaching of said members a canalisation of thelines of force is obtained.

2. In an electromagnet, an excitin circuit, a core member, and anarmature member arranged to approach each other when said excitingcircuit is closed, at least one of said members having, parts ofrectangular axial section, arranged in steps, gradually diminishingtowards the end of said member, and portions comprising surfacesinclined with regard to the axis of said armature member andinterconnecting said parts.

3. In an electromagnet, an exciting circuit, a core member, and anarmature member arranged to approach each other when said excitingcircuit is closed, at least one of said members having, parts ofrectangular axial section arranged in steps, gradually diminishingtowards the end of said member, and portions comprising surfacesinclined by 45 with regard to the axis of said armature member andinterconnecting said parts.

4. In an electromagnet, an exciting circuit, a core member, and anarmature member arranged to approach each other when said excitingcircuit is closed, one of said members having outer staggered surfacesgradually diminishing towards the end of said member, the other of saidmembers comprising a hole staggered correspondingly to said staggeredsurfaces, said staggered surfaces and said staggered hole being disposedin such mutual cooperating position that during the mutual approachingof said members a canalisation of the lines of forces is obtained.

'5. In an electromagnet, an exciting coil comprising differentconcentrical windings, a core member, and an armature member arranged toapproach each other when one of said windings is closed, at least one ofsaid members having a number of relatively fixed parts arranged in stepsand comprising surfaces gradually diminishing towards the end of saidmember, said member being disposed with regard to the other member insuch a cooperating position that during the mutual approaching of saidmembers a canalisation of the lines of force is obtained.

6. In an electromagnet, an exciting circuit, a core member, and anarmature member arranged to approach each other when said excitingcircuit is closed, one of said members having outer staggered surfacesgradually diminishing towards the end of said member, the other of saidmembers comprising a hole staggered correspondingly to said staggeredsurfaces, said staggered surfaces and said staggered hole being disposedin such mutual cooperating position that during the mutual approachingof said members, a canalisation of the lines of force is obtained, aguide on one of said members, and a rod slidably entering said guide toguarantee mutual concentricity of said members.

7. In an electromagnet, an exciting circuit, a core member, and anarmature member arranged to approach each other when said excitingcircuit is closed, one of said members having outer staggered surfacesgradually diminishing towards the end of said member, the other of saidmembers comprising a hole staggered correspondingly to said staggeredsurfaces, said staggered surfaces and said staggered hole being disposedin such mutual cooperating position that during the mutual approachingof said members a canalisation of the lines of force is obtained, and asaturation flange on at least one of said members destined to thepassage of the magnetic flux between said members.

8. In an electromagnet, an exciting circuit, a core member, an armaturemember arranged to approach each other when said exciting circuit isclosed, one of said members having outer relatively fixed staggeredsurfaces gradually diminishing towards the end of said member, the otherof said members comprising a hole staggered correspondingly to saidstaggered surfaces, said staggered surfaces and said staggered holebeing disposed in such mutual cooperating position that during themutual approaching of said members a canalisation of the lines of forceis obtained, a guide on one of said members, a rod slidably enteringsaid guide to guarantee mutual concentricity of said members, and aswitch arranged to vary the exciting current and to be controlled bysaid rod.

9. In an electromagnet, an exciting circuit, a fixed core member, amovable armature member arranged to approach said core member when saidexciting circuit is closed, at least one of said members having a numberof parts arranged in relatively fixed steps and comprising surfacesgradually diminishing towards the end of said member, said armaturemember being disposed with regard to said core member in such acooperating position that during the approaching of said armature membera canalisation of the lines of force is obtained, and a shoulder on saidarmature member destined to come into contact with said fixed coremember outside of the concentration of the lines of force, forestablishing an air gap acting against the remanence in said members.

10. In an electromagnet, an exciting coil comprising a number ofconcentrical windings, a core member, and an armature member arranged toapproach each other when one of said windings is closed, at least one ofsaid members having a number of parts corresponding to the number ofsaid concentrical windings and arranged in steps and comprising surfacesgradually diminishing towards the end of said member, said member beingdisposed with regard to the other member in such a cooperating positionthat during the mutual approaching of said members a canalisa tion ofthe lines of force is obtained.

11. In an electromagnet, an exciting coil comprising a number ofconcentrical windings, a core member, an armature member arranged toapproach each other when one of said windings is closed, at least one ofsaid members having a number of parts corresponding to the number ofsaid concentrical windings and arranged in steps and comprising surfacesgradually diminishing towards the end of said member, said member beingdisposed with regard to the other member in such a cooperating positionthat during the mutual approaching of said members a canalisation of thelines of force is obtained, and a switching device arranged to allow theinner of said concentrical windings of being at first excited and thenone after the other of said concentrical windings following one anothertowards the outside until the entire coil is excited.

12. In an electromagnet according to claim 1, an adjustable resistancein series with said'exciting circuit.

13. In an electromagnet according to claim 1, a resistance in serieswith said exciting circuit and adjustable by the movement of saidarmature member.

ERNEST ALPHONSE DERUNGS.

